The Snow Geese breed as far north as any goose, they reach 82°N on Ellesmere Island in Canada and northwestern Greenland. Their heads and necks are stained rusty-brown or orange-yellow due to grubbing for roots in iron-rich mud. Two races are nearly identical, but the larger, bulkier, thicker-necked Greater Snow Geese (A. c. atlanticus) weight 6-10.5 pounds, compared to 4-6.25 pounds for Lesser Snow Geese (A. c. caeurulescens). The larger birds generally exceeds 2.4 inches in length. Snow Geese feed primarily ashore. They are essentially rooters and grubbers. Many winter in coastal salt marshes and tidal areas, where their especially heavy bill is suited for gripping and tearing out rhizomes from estuarine mud. The geese breed mostly in Arctic Canada, some Lesser Snow Geese nest in northeastern Siberia as well, but all Russian birds winter in California. While goslings are polymorphic, Snow Goose offspring invariably all fledge as white birds, whereas Blue Geese progeny are dark. Goslings imprint on their parents early in life and are inclined to select mates of the same colour, even in mixed colonies, the blue-and-white components remain fairly discrete. Nevertheless, mixed pairs are not usual, resulting in goslings of either colour, but as the dark colour predominates, some colonies presently consist of mostly Blue Geese. White geese tend to lose more eggs to predators, perhaps because they nest slightly earlier, and the birds are less conspicuous if snows melts early. Snow Geese arrive on the Arctic tundra in May before the snow and ice has completely melted. Their 22-25 day incubation period ranks among the shortest of all geese. They forage up to 18-20 hours a day. Goslings grow quite rapidly and some are airborne in over five weeks. Snow Geese migrate in aggregations of their own kind. Many pause along the way to feed. The majority of Lesser Snow Geese winter in Texas, whereas the larger race gravitates to the Atlantic coast from New Jersey south to North Carolina.